Subzero: Fixed deadlock with _start but no globals

src/IceInstrumentation.cpp

Index: src/IceInstrumentation.cpp
diff --git a/src/IceInstrumentation.cpp b/src/IceInstrumentation.cpp
index 0cd218abcbdbd7df2507cab8808dbcfdb7db5c20..0709bfce2d3ba370a00b7c4a0cbe7a5cbde1164c 100644
--- a/src/IceInstrumentation.cpp
+++ b/src/IceInstrumentation.cpp
@@ -118,4 +118,18 @@ void Instrumentation::instrumentInst(LoweringContext &Context) {
   }
 }
 
+void Instrumentation::setHasSeenGlobals() {
+  {
+    std::unique_lock<std::mutex> _(GlobalsSeenMutex);
+    HasSeenGlobals = true;
+  }
+  GlobalsSeenCV.notify_all();
+}
+
+LockedPtr<VariableDeclarationList> Instrumentation::getGlobals() {
+  std::unique_lock<std::mutex> GlobalsLock(GlobalsSeenMutex);
+  GlobalsSeenCV.wait(GlobalsLock, [this] { return HasSeenGlobals; });
+  return Ctx->getGlobals();
+}
+
 } // end of namespace Ice